Is there an AI model for generating sarcastic sentences?
A simple form of sarcasm involves a direct reversal of the literal meaning of the statement, eg "Great weather we're having" (during a thunderstorm), "just what I needed" (when something goes wrong).

The problem with doing this in random sentences is that you may have no context to establish the reversal of the literal meaning.

You could possibly construct them by using a template along the lines of "Just what I needed - (random bad thing happened) today"

Or, when an outcome of a process is calculated, if it is not the desired outcome, instead of returning "mission unsuccessful" or "mission not yet complete", the AI could say "you're having a great day, aren't you? - mission unsuccessful" or "great work, genius - mission not yet complete".

Most random sentences will not be suitable for sarcasm, so it could only be applied in specific circumstances. 

It is not clear from your question what the context is for these random sentences, and therefore it is not clear whether that context would be suitable for sarcasm at all.